Electric Night Photos: ISO 80 versus ISO800

I tried to pick and exciting sounding title! These are some more of my thoughts on railroad night photography, the nuts and the bolts:

The other evening at Clontarf Road in Dublin, I was experimenting with various ISO settings in preparation for a more serious photo I was about to expose under the wires on Irish Rail.

Normally with my Lumix LX7, I limit the ISO settings to between 80 and 200, because this camera tends to get noticeably noisy/grainy at the higher settings.

Higher ISO increases the effective sensitivity of the sensor but does so at the expense of image quality, especially in regards to exposure latitude and noise. (Technically that’s not exactly correct, but for the sake of space and clarity that’s how I’m going to explain it here.)

In my night situation using a higher ISO setting will allow me a faster maximum shutter speed, which I need to stop a train in motion. Yet with each one-stop increment the image quality suffers more severely.

Keep in mind with each doubling of the ISO, the camera gains one stop: So, ISO 100 to 200 is one stop, 200 to 400 one stop, etc; and each jump allows an equivalent one stop increase in shutter speed. So in the lighting conditions at my location and using my LX7 aperture set at f1.4, ISO 100 allowed 1/15 of a second; ISO 200 1/30th; ISO 400 1/60th; ISO 800 1/125. Obviously, I needed to go higher than ISO 200 to stop the action. (Or simply pan the train, but that’s a story for another post).

Here are two views of static DART electric trains in low light that I made simply as comparison tests to see how the higher ISO setting compared visually. (Ignore the minor variations in composition).

At the small size displayed for internet viewing there’s only a slight difference. One is at the camera’s minimum ISO setting which is 80; the other is at 800, which three and a third stops faster.